Opinions?
Like many on this board, I've been shooting, carrying and instructing firearms for a good while - And we will all likely still have different answers for you

(Opinions. Just like belly buttons. We all have 'em.), but here I goes anywho: Bottom line is "Your gun – Your choice". What you have to evaluate is
your own skills, life style, needs and comforts.
I shoot/carry both revolvers and pistols (usually alternately), but I've spent near a lifetime handling/carrying/using both. I favor shoulder holsters for concealment, closely followed by on the belt (OWB and IWB), then pocket carry, and I avoid ankle carry. This suits my skills, life style, needs and comforts.
Not knowing much about you or your training, I can only go with my typical recommendation for folks new to this concealed handgun game:
Get additional training, and lots of practice.
This needs to be the best training (including use of force training) and best practice you can afford. I have over forty years of training and practice - most very good though some was a mistake – and I still don't think I've had enough.
Revolver or Pistol?
You have to know which one you're most comfortable with, not what I'm comfortable with. Both have advantages and disadvantages. I do tend to favor revolvers for new shooters (they're even good for well seasoned shooters also). I have carried revolvers on duty and would again if they let me, but I'm also very comfortable carrying a pistol instead. I believe revolvers do require fewer manipulation skills (especially if there is a malfunction), but one can develop the additional manipulation skills for a pistol easily enough.
Where one lives, travels or works may make a difference though in my recommendation. If they had to deal with a reasonable likelihood of serious criminal activity with multiple threats (such as when I was in parts of Central America), I'd likely recommend a high capacity pistol instead to that same new shooter.
Find a range that rents guns, find a friend that has something for you to try out, or go to a decent gun club with a range and see if they have anyone that would be willing to help you out (I've been pleasantly surprised just how willing other shooters have been to let me try out their guns or offer advice and even training – I often have used some of my own range time to assist another shooter, especially a new shooter).
Mode of Carry.
Definitely requires an assessment of your skills, life style, needs and comforts. Example: If you usually wear only shorts and a polo shirt you won't have as many options as if you normally wear a suit with jacket.
At the minimum the holster needs to be of good quality, secure in how it retains the gun and in staying in place, and reasonably accessible (even deep concealment holsters need to be as accessible as possible). If worn on a belt, the belt needs to be of good quality, and stiff and wide enough to keep the holster from shifting or sagging.
Caliber/Ammo
I could start an ammo topic war if I try to be too specific. I've gone through most of the normal phases of caliber/ammo choices and have settled on the following basic rule:
"Shot placement is King, adequate penetration is Queen, and everything else is Angels dancing on the head of a pin."
Only hits that reach in and disrupt something important are important. If you can do that better with a 9mm or .38 Spl than you can with a .45 acp or .44 Mag then the 9 or the 38 are better choices for you.
I personally like big 40 – 45 caliber bullets or the .357 Mag and shoot them well, but I have a few guns that I can shoot very well in 9 and 38 so I often carry one of these instead (in fact fairly often). Big bullets can (not will, but can) make bigger holes that go in deep, but with the right (good construction, velocity and with decent mass) smaller cartridge/load you can get the job done more than well enough if they're placed well enough.
The first criterion is for you to find the cartridge that you shoot well, under stress, repeatedly (quick follow-up while maintaining your accuracy). Then search for the best defensive loading in that one.
This above may not have been what you were looking for, but I think it's a good place to start.
At your service,